Opportunistic viral infections are prevalent in patients with acquired immune deficiency syndrome (AIDS). To investigate the possibility that opportunistic infections in the herpesvirus group might induce expression from the human T-lymphotropic virus type III (HTLV-III) long-terminal repeats (LTR), we constructed permanent cell lines (murine and simian), containing the HTLV-III LTR directing the chloramphenicol acetyltransferase (CAT) gene. Whereas in transient gene expression assays, the HTLV-III LTR express CAT activity as high as the simian virus-40 (SV40) early promoter, no CAT activity is observed after chromatin integration in permanent cell lines. Superinfection of these latent HTLV-III LTR containing lines with herpes viruses reactivated the HTLV-III LTR as determined by S1 nuclease RNA analysis. Whereas simian virus-40 (SV40) and adenovirus infection of the latent HTLV-III LTR containing cell lines did not activate HTLV- III LTR expression. Reactivation of latent HTLV-III LTR transcription is also observed after 5 azacytidine, cycloheximide and UV irradiation treatments. Run-on transcription in isolated nuclei, suggests that the activation is on the transcriptional level. Activation by herpes simplex virus type 1 (HSV-1) required viral immediate early (IE) gene expression as determined by virus infection in the presence of cycloheximide and with mutants defective in viral gene expression. The long-term objective of the research described in this proposal is to elucidate the mechanism(s) by which the HTLV-III LTR could be activated on the transcriptional level. The specific aims are to identify the viral gene products responsible for latent HTLV-III LTR transcription activation; to establish permanent cell lines in human B and T-cells containing the HTLV-III LTR; to identify the mechanism(s) of repression of the HTLV-III regulatory region and to define the HTLV-III LTR DNA sequences involved repression and reactivation. The preliminary results suggest that opportunistic infection of the herpesvirus group could induce HTLV-III expression in individuals harboring the virus in a latent form and points to the potential of these cell lines to study the affects of other physiochemical stimuli on HTLV-III reactivation.